What happened
On May 11, 2008, a Beechcraft BE77 Skipper, registered EI-BHT, departed from Ireland West, Knock Airport (EIKN) at 15:35 UTC, bound for Weston Aerodrome (EIWT). Roughly seven minutes into the flight, the pilot notified air traffic control of engine vibrations. This was followed by reports of limited engine power and an inability to maintain the aircraft's altitude.
As the aircraft struggled to stay airborne, the pilot attempted an emergency landing in the rugged terrain of Kilmovee, County Mayo. Eyewitnesses at the scene observed the engine laboring before it ceased operation; the engine reportedly attempted to restart briefly before failing completely just moments before the impact. The accident resulted in one fatality and one serious injury. The aircraft was destroyed upon impact.
The investigation
Investigators examined the wreckage on-site and noted that the propeller did not show evidence of rotation at the time of impact. A subsequent detailed strip examination of the engine was performed at the AAIU facility in Gormanston.
This technical inspection revealed significant damage to the engine's internal components. Specifically, the inlet valves in both Cylinder No. 2 and Cylinder No. 3 exhibited radial cracking that originated at the valve seat and extended toward the stems. Furthermore, a portion of the inlet valve from Cylinder No. 2 had broken off and migrated into Cylinder No. 4.
Findings
- The engine experienced a mechanical failure characterized by radial cracking of the inlet valves in two cylinders.
- A fragment of an inlet valve from Cylinder No. 2 was found lodged in Cylinder No. 4.
- The precise origin and cause of the radial cracking in the valves remain undetermined and require further investigation.